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Canonical Wnt/β-catenin signaling regulates the activation of the myogenic determination gene Myf5 at the onset of myogenesis, but the underlying molecular mechanism is unknown. Here, we report that the Wnt signal is transduced in muscle progenitor cells by at least two Frizzled (Fz) receptors (Fz1 and/or Fz6), through the canonical β-catenin pathway, in the epaxial domain of newly formed somites. We show that Myf5 activation is dramatically reduced by blocking the Wnt/β-catenin pathway in somite progenitor cells, whereas expression of activated β-catenin is sufficient to activate Myf5 in somites but not in the presomitic mesoderm. In addition, we identified Tcf/Lef sequences immediately 5' to the Myf5 early epaxial enhancer. These sites determine the correct spatiotemporal expression of Myf5 in the epaxial domain of the somite, mediating the synergistic action of the Wnt/β-catenin and the Shh/Gli pathways. Taken together, these results demonstrate that Myf5 is a direct target of Wnt/β-catenin, and that its full activation requires a cooperative interaction between the canonical Wnt and the Shh/Gli pathways in muscle progenitor cells. [ABSTRACT FROM AUTHOR]

Understanding the host immune response during cryptococcal meningitis (CM) is of critical importance for the development of immunomodulatory therapies. We profiled the cerebrospinal fluid (CSF) immune-response in ninety patients with HIV-associated CM, and examined associations between immune phenotype and clinical outcome. CSF cytokine, chemokine, and macrophage activation marker concentrations were assayed at disease presentation, and associations between these parameters and microbiological and clinical outcomes were examined using principal component analysis (PCA). PCA demonstrated a co-correlated CSF cytokine and chemokine response consisting primarily of Th1, Th2, and Th17-type cytokines. The presence of this CSF cytokine response was associated with evidence of increased macrophage activation, more rapid clearance of Cryptococci from CSF, and survival at 2 weeks. The key components of this protective immune-response were interleukin (IL)-6 and interferon-γ, IL-4, IL-10 and IL-17 levels also made a modest positive contribution to the PC1 score. A second component of co-correlated chemokines was identified by PCA, consisting primarily of monocyte chemotactic protein-1 (MCP-1) and macrophage inflammatory protein-1α (MIP-1α). High CSF chemokine concentrations were associated with low peripheral CD4 cell counts and CSF lymphocyte counts and were predictive of immune reconstitution inflammatory syndrome (IRIS). In conclusion CSF cytokine and chemokine profiles predict risk of early mortality and IRIS in HIV-associated CM. We speculate that the presence of even minimal Cryptococcus-specific Th1-type CD4+ T-cell responses lead to increased recruitment of circulating lymphocytes and monocytes into the central nervous system (CNS), more effective activation of CNS macrophages and microglial cells, and faster organism clearance; while high CNS chemokine levels may predispose to over recruitment or inappropriate recruitment of immune cells to the CNS and IRIS following peripheral immune reconstitution with ART. These results provide a rational basis for future studies of immune modulation in CM, and demonstrate the potential of baseline immune profiling to identify CM patients most at risk of mortality and subsequent IRIS.

In the absence of a protective vaccine against human immunodeficiency virus (HIV), there is an urgent need for the development of effective topical microbicides to prevent HIV infection. Candidate vaginal microbicides should provide protection against circulating strains, be cheap, stable on storage, safe and easy to use. Here we describe a detailed study of the safety and efficacy of Cyanovirin-N (CV-N) in vitro, and in an ex vivo model of female genital tissue explants. CV-N demonstrated potent activity in the low nanomolar range against laboratory and primary isolates. Activity was related to the affinity of CV-N for binding to whole virions as determined by acoustic resonance. Potent activity was also observed against cell-associated HIV-1, although slightly reduced. CV-N activity in the presence of whole semen was reduced by 7-10-fold, although it remained in the low nanomolar range and was minimally modified by the presence of Candida albicans. Furthermore, CV-N potently inhibited infection of ectocervical explants and virus dissemination by tissue-emigrating cells. In peripheral blood mononuclear cell (PBMC) assays, CV-N was shown to have some mitogenic activity following 3 days exposure to compound, and this was associated with a modest increase in expression of gamma interferon, stromal cell-derived factor 1beta and interleukin 4. However, 2 h exposure to CV-N had no effect on cytokine expression in PBMC or tissue explant culture over a 24 h period, suggesting that the potential for inflammation is low. Data presented here indicate that targeting HIV envelope glycoproteins may provide an effective strategy to prevent HIV-1 infection mediated by either cell-free virus or infected cells.

Genetic immunization using viral vectors provides an effective means to elicit antigen-specific cellular immune responses. Several viral vectors have proven efficacious in inducing immune responses after direct injection in vivo. Among them, recombinant, self-inactivating lentiviral vectors are very attractive delivery systems, as they are able to efficiently transduce into and express foreign genes in a wide variety of mammalian cells. A self-inactivating lentiviral vector was evaluated for the delivery of human immunodeficiency virus 1 (HIV-1) envelope sequences in mice in order to elicit specific immune responses. With this aim, BALB/c mice were immunized with a single injection of self-inactivating lentiviral vectors carrying either the full-length HIV-1(HXB2) Rev/Env (TY2-IIIBEnv) or the codon-optimized HIV-1(JR-FL) gp120 (TY2-JREnv) coding sequence. Both vectors were able to elicit specific cellular responses efficiently, as measured by gamma interferon ELISPOT and chromium-release assays, upon in vitro stimulation of splenocytes from BALB/c immunized mice. However, only the TY2-JREnv-immunized mice were able to elicit specific humoral responses, measured as anti-gp120 antibody production. These data provide the first evidence that a single, direct, in vivo administration of a lentiviral vector encoding a viral gene might represent a useful strategy for vaccine development.